Pbelkner's decision to write incompatible data has been criticized numerous times. It's like the guy doesn't even understand the problem of his decision. I could support use of REPLAYGAIN_ALGORITHM tag to let users and software know what tool generated the numbers but I see no reason to store any other data. Reference level must be 89 dB SPL as stated in the specs. If user wishes to use other target level he flips a switch in his player (switch being for example preamp slider, could be a dropdown menu to select R128 or ATSC or anything).I recall original ReplayGain spec suggested storing the algorithm too and perhaps even the fact that user had manually altered the numbers. Perhaps manual adjustment could be identified by storing something like REPLAYGAIN_ALGORITHM=manual.